U.S. patent number 5,720,261 [Application Number 08/348,537] was granted by the patent office on 1998-02-24 for valve controller systems and methods and fuel injection systems utilizing the same.
This patent grant is currently assigned to Oded E. Sturman. Invention is credited to Steven Massey, Christopher North, Robert Strom, Oded E. Sturman.
United States Patent |
5,720,261 |
Sturman , et al. |
February 24, 1998 |
Valve controller systems and methods and fuel injection systems
utilizing the same
Abstract
The present invention is a fuel injection system having one or
more fuel injectors and an electronic control system therefore. The
preferred fuel injector has a double magnetic latching solenoid
three-way or four-way spool valve that controls the flow of a
working fluid that is used to control the discharge of fuel into
the combustion chamber or intake manifold of an engine through the
nozzle of the injector. The control system provides actuating
current pulses to each of the solenoids to actuate and latch the
solenoids to effect initiation and termination of the injection.
Disclosed are control systems that provide a snap action in one or
both actuating directions of the valve by electromagnetically
retaining the valve in the latched condition until the force in the
actuated solenoid builds to a high level, and then releasing the
valve for higher acceleration to the actuated position. Also
disclosed is an exemplary control system that senses the arrival of
valve at the actuated position so that the actuating current pulse
can be terminated as soon as possible so as to allow a strong
current pulse drive, but of low total energy, for fast actuation of
a relatively small valve. Other embodiments, features and uses of
the invention are disclosed.
Inventors: |
Sturman; Oded E. (Newbury Park,
CA), North; Christopher (Camarillo, CA), Strom;
Robert (Thousand Oaks, CA), Massey; Steven (Camarillo,
CA) |
Assignee: |
Sturman; Oded E. (Woodland
Park, CO)
|
Family
ID: |
23368460 |
Appl.
No.: |
08/348,537 |
Filed: |
December 1, 1994 |
Current U.S.
Class: |
123/446;
123/467 |
Current CPC
Class: |
F02M
59/105 (20130101); F02M 59/466 (20130101); F02D
41/20 (20130101); F02M 57/025 (20130101); F02D
2041/2017 (20130101); F02D 2041/2027 (20130101); F02D
2041/2034 (20130101); F02D 2041/2075 (20130101); F02D
2041/2079 (20130101) |
Current International
Class: |
F02M
59/10 (20060101); F02M 57/02 (20060101); F02M
57/00 (20060101); F02M 59/46 (20060101); F02D
41/20 (20060101); F02M 59/00 (20060101); F02M
051/06 () |
Field of
Search: |
;123/446,467,472,490,299,300,458,497,498,499 ;251/129.1,12.01
;239/585.4,88,90,92,96 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
264710 |
|
Jan 1950 |
|
DE |
|
2209206 |
|
Aug 1973 |
|
DE |
|
4-341653 |
|
Apr 1992 |
|
JP |
|
349165 |
|
May 1931 |
|
GB |
|
892121 |
|
Mar 1962 |
|
GB |
|
Primary Examiner: Miller; Carl S.
Attorney, Agent or Firm: Blakely, Sokoloff, Taylor &
Zafman LLP
Claims
I claim:
1. A fuel injection system comprising:
a fuel injector;
an injector valve member for coupling to a source of fluid under
pressure, the injector valve member being coupled to the fuel
injector;
a first solenoid coil for magnetically moving the valve member to a
first position for causing fuel injection by the fuel injector
responsive to an actuating current in the first solenoid coil;
a second solenoid coil for moving the valve member to a second
position for stopping fuel injection by the fuel injector
responsive to an actuating current in the second solenoid coil;
an electronic control system coupled to the first and second
solenoid coils for providing current to the first and second
solenoid coils to control the position of the valve member to
initiate and terminate fuel injection by the injector, the control
system including a sensing circuit coupled to one of the solenoid
coils for sensing the valve member reaching the position caused by
the current in the other solenoid coil and for terminating the
current in the respective one of the solenoids responsive
thereto.
2. The fuel injection system of claim 1 wherein the valve member is
a spool valve member.
3. The fuel injection system of any one of claims 1 or 2 wherein
the valve member tends to remain in the first position by residual
magnetism as the current in the first solenoid coil reduces toward
zero and in the second position by residual magnetism as the
current in the second solenoid coil reduces toward zero.
4. The fuel injection system of claim 3 wherein the residual
magnetism is at least in part the residual magnetism of the valve
member.
5. The fuel injection system of claim 1 further comprised of means
responsive to the actuation time between applying a current to a
solenoid coil and the valve member reaching the position caused by
the current in the respective solenoid coil for monitoring the
variation in the actuation times for successive operating cycles of
the fuel injection system.
6. The fuel injection system of claim 1 further comprised of a
second sensing circuit coupled to the other of the solenoid coils
for also sensing the valve member reaching the position caused by
the current in the opposite solenoid coil and for terminating the
current in the respective one of the solenoids responsive
thereto.
7. The fuel injection system of any one of claims 1 or 6 wherein
the electronic control system will temporarily provide a holding
current to one of the solenoid coils to hold the valve member in
its then present position as actuation current is applied to the
other solenoid coil, then will terminate the holding current to
release the valve member for actuation.
8. The fuel injection system of claim 7 wherein the electronic
control system will temporarily provide a holding current to either
of the solenoid coils to hold the valve member in its then present
position as actuation current is applied to the other solenoid
coil, and will terminate the holding current to release the valve
member for actuation.
9. The fuel injection system of any one of claims 2, 5 or 6 wherein
the electronic control system is microprocessor controlled.
10. The fuel injection system of claim 9 wherein the electronic
control system includes sensors for responding to operating
conditions of an engine, the microprocessor being responsive to
sensors to control the position of the valve member to initiate and
terminate fuel injection by the injector.
11. The fuel injection system of claim 9 wherein the electronic
control system includes sensors for responding to environmental
conditions, the microprocessor being responsive to sensors to
control the position of the valve member to initiate and terminate
fuel injection by the injector.
12. The fuel injection system of claim 9 wherein the electronic
control system includes sensors for responding to operating
conditions of an engine and environmental conditions, the
microprocessor being responsive to the sensors to control the
position of the valve member to initiate and terminate fuel
injection by the injector.
13. A fuel injection system comprising:
a fuel injector;
an injector valve member for coupling to a source of fluid under
pressure, the injector valve member being coupled to the fuel
injector;
a first solenoid coil for magnetically moving the valve member to a
first position for causing fuel injection by the fuel injector
responsive to an actuating current in the first solenoid coil;
a second solenoid coil for moving the valve member to a second
position for stopping fuel injection by the fuel injector
responsive to an actuating current in the second solenoid coil;
an electronic control system coupled to the first and second
solenoid coils for providing current to the first and second
solenoid coils to control the position of the valve member to
initiate and terminate fuel injection by the injector, the control
system temporarily providing a holding current to one of the
solenoid coils to hold the valve member in its then present
position as actuation current is applied to the other solenoid
coil, and then terminating the holding current to release the valve
member for actuation.
14. The fuel injection system of claim 13 wherein the valve member
is a spool valve member.
15. The fuel injection system of claim 14 wherein the valve member
tends to remain in the first position by residual magnetism as the
current in the first solenoid coil reduces toward zero and in the
second position by residual magnetism as the current in the second
solenoid coil reduces toward zero, in part by the residual
magnetism of the valve member.
16. The fuel injection system of claim 13 further comprised of
means responsive to the actuation time between applying a current
to a solenoid coil and the valve member reaching the position
caused by the current in the respective solenoid coil for
monitoring the variation in the actuation times for successive
operating cycles of the fuel injection system.
17. The fuel injection system of claim 13 wherein the electronic
control system coupled to the first and second solenoid coils will
temporarily provide a holding current to either of the solenoid
coils to hold the valve member in an actuated position as actuation
current is applied to the other solenoid coil, then will terminate
the holding current to release the valve member for actuation.
18. The fuel injection system of claim 17 further comprising a
sensing circuit coupled to one of the solenoid coils for sensing
the valve member reaching the position caused by the current in the
other solenoid coil and for terminating the current in the
respective one of the solenoids responsive thereto.
Description
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to the field of valve controllers in
systems and methods, and fuel injection systems utilizing the
same.
(2) Prior Art
Fuel injectors are used to introduce pressurized fuel either
directly into the combustion chamber of an internal combustion
engine or, alternatively, into the intake manifold adjacent to the
inlet valve of each cylinder. FIG. 1 shows a fuel injection system
10 of the prior art as used for diesel injection directly into the
combustion chamber of a diesel engine. The injection system
includes a nozzle 12 that is coupled to a fuel port 14 through an
intensifier chamber 16. The intensifier chamber 16 contains an
intensifier piston 18 which reduces the volume of the chamber 16
and increases the pressure of the fuel therein. The pressurized
fuel is released into a combustion chamber through the nozzle
12.
The intensifier piston 18 is stroked by a working fluid that is
controlled by a poppet valve 20. The working fluid enters the valve
through port 22. The poppet valve 20 is coupled to a solenoid 24
which can be energized to pull the valve into an open position. As
shown in FIG. 2, when the solenoid 24 opens the poppet valve 20,
the working fluid applies a pressure to the intensifier piston 18.
The pressure of the working fluid moves the piston 18 and
pressurizes the fuel. When the solenoid 24 is deenergized, springs
26 and 28 return the poppet valve 20 and the intensifier piston 18
back to the original positions.
Spring return fuel injectors are relatively slow because of the
slow response time of the poppet valve return spring. Additionally,
the spring rate of the spring generates an additional force which
must be overcome by the solenoid. Consequently the solenoid must be
provided with enough current to overcome the spring force and the
inertia of the valve. Higher currents generate additional heat and
degrade the life and performance of the solenoid. Furthermore, the
spring rate of the springs may change because of creep and fatigue.
The change in spring rate will create varying results over the life
of the injector.
Conventional fuel injectors typically incorporate a mechanical
feature which determines the shape of the fuel curve. Mechanical
rate shapers are relatively inaccurate and are susceptible to wear
and fatigue. Additionally, fuel leakage into the spring chambers of
the nozzle and the intensifier may create a hydrostatic pressure
that will degrade the performance of the valve.
The graph of FIG. 3 shows an ideal fuel injection rate for a fuel
injector. To improve the efficiency of the engine, it is desirable
to pre-inject fuel into the combustion chamber before the main
discharge of fuel. As shown in phantom, the fuel curve should
ideally be square so that the combustion chamber receives an
optimal amount of fuel. Actual fuel injection curves have been
found to be less than ideal, thereby contributing to the
inefficiency of the engine. It is desirable to provide a high speed
fuel injector that will supply a more optimum fuel curve than fuel
injectors in the prior art.
As shown in FIGS. 1 and 2, the poppet valve constantly strikes the
valve seat during the fuel injection cycles of the injector.
Eventually the seat and the poppet valve will wear, so that the
valve is not properly seated within the valve chamber. Improper
valve seating may result in an early release of the working fluid
into the intensifier chamber, causing the injector to prematurely
inject fuel into the combustion chamber. It would be desirable to
provide an injector valve that did not create wear between the
working fluid control valve and the associated valve seat of the
injector.
The solenoid 24 of the fuel injector of FIGS. 1 and 2 is a direct
pull solenoid operating in opposition to spring 26. This is an
advantage over still earlier prior art fuel injectors which were
cam operated in that the solenoid operated injectors of FIGS. 1 and
2 may be electronically controlled in timing and duration, unlike
the cam operated injectors wherein at least the initiation of
injection was typically at a fixed angle of rotation of the
crankshaft independent of engine speed or load. The solenoid
operated injectors of FIG. 1 and 2 have the disadvantage however,
of not being as fast as they could be, and of consuming more power
than necessary. In particular, since the solenoids operate in
opposition to spring 26, the net force controlling the speed of
opening of the poppet valve 20 is not the solenoid force, but
rather the difference between the solenoid force and spring force
26, whereas the net force closing the valve is simply the spring
force 26, which can only be a fraction of the solenoid opening
force for the valve to operate. Accordingly, the full pulling
potential of the solenoid is not realized on either opening or
closing of the poppet valve. Also, the solenoid must remain
energized for as long as the solenoid is actuated, and thus must be
of a size and of a heat dissipation capability commensurate with a
"full throttle" fuel injection rate. Further, the solenoid pulling
force must be adequate to properly operate the valve at the lower
extreme of the power supply and upper extremes of solenoid coil
resistance, the force of spring 26, etc. while at the same time not
overheating at full throttle, upper power supply voltage and low
solenoid coil resistance extremes. It is the improvement of
performance in this area, among other things, to which the present
invention is directed.
BRIEF SUMMARY OF THE INVENTION
The present invention is a fuel injection system having one or more
fuel injectors and an electronic control system therefore. The
preferred fuel injector has a double magnetic latching solenoid
three-way or four-way spool valve that controls the flow of a
working fluid that is used to control the discharge of fuel into
the combustion chamber or intake manifold of an engine through the
nozzle of the injector. The control system provides actuating
current pulses to each of the solenoids to actuate and latch the
solenoids to effect initiation and termination of the injection.
Disclosed are control systems that provide a snap action in one or
both actuating directions of the valve by electromagnetically
retaining the valve in the latched condition until the force in the
actuated solenoid builds to a high level, and then releasing the
valve for higher acceleration to the actuated position. Also
disclosed is an exemplary control system that senses the arrival of
valve at the actuated position so that the actuating current pulse
can be terminated as soon as possible so as to allow a strong
current pulse drive, but of low total energy, for fast actuation of
a relatively small valve. Other embodiments, features and uses of
the invention are disclosed.
BRIEF DESCRIPTION OF THE DRAWINGS
The objects and advantages of the present invention will become
more readily apparent to those ordinarily skilled in the art after
reviewing, the following detailed description and accompanying
drawings, wherein:
FIG. 1 is a cross-sectional view of a fuel injector of the prior
art;
FIG. 2 is a cross-sectional view similar to FIG. 1, showing the
fuel injector injecting fuel;
FIG. 3 is a graph showing the ideal and actual fuel injection
curves for a fuel injector;
FIG. 4 is a cross-sectional view of a fuel injector with a four-way
control valve that has a spool valve in a first position;
FIG. 5 is a cross-sectional view of the fuel injector with the
spool valve in a second position;
FIG. 6 is an alternate embodiment of the fuel injector of FIG.
4;
FIG. 7 is a cross-sectional view of an alternate embodiment of a
fuel injector which has a three-way control valve.
FIG. 8 is a circuit diagram for a basic valve controller in
accordance with the present invention.
FIG. 9 illustrates the connection of the circuit of FIG 8 to the
coils 202 and 200 of the two solenoids 138 and 140 of FIG. 4.
FIG. 10 illustrates a typical control signal waveform.
FIG. 11 illustrates a typical current pulse in a solenoid coil of
the present invention as driven by the circuit if FIG. 8.
FIGS 12A-C show a circuit diagram for another controller circuit of
the present invention.
FIG. 13 illustrates the connection of the circuit of FIG. 12 to the
coils 202 and 200 of the two solenoids 138, and 140 of FIG. 4.
FIGS. 14A-C show is a circuit diagram for a still further control
circuit in accordance with the present invention.
FIG. 15 is a copy of a strip chart showing the current waveform in
an actuated solenoid and the back EMF measured on the coil of the
solenoid which had previously been latched in accordance with the
present invention.
FIG. 16 is a copy of a strip chart showing the current waveform in
an actuated solenoid and the back EMF measured on the coil of the
solenoid which had previously been latched in accordance with the
present invention for an embodiment wherein the current pulse is
terminated upon arrival of the spool valve at the actuated
position.
FIG. 17 is a block diagram of one embodiment of fuel injection
system in accordance with the present invention.
FIG. 18 is a block diagram of an alternate embodiment of fuel
injection system in accordance with the present invention.
FIG. 19 is a block diagram of a circuit connected to the battery
supply line for the injection system so that when the battery
voltage as supplied to the injection system falls below some
predetermined limit, the circuit will enable the operation of a
step-up switching regulator which in turn provides a stepped up and
regulated output voltage VOUT to a valve supply switching
circuit.
FIG 20 is a circuit diagram for the block diagram of FIG. 19.
DETAILED DESCRIPTION OF THE INVENTION
Referring to the drawings more particularly by reference numbers,
FIGS. 4 and 5 show a fuel injector 50 of the present invention. The
fuel injector 50 is typically mounted to an engine block and
injects a controlled pressurized volume of fuel into a combustion
chamber (not shown). The injector 50 of the present invention is
typically used to inject diesel fuel into a compression ignition
engine, although it is to be understood that the injector could
also be used in a spark ignition engine or any other system that
requires the injection of a fluid.
The fuel injector 10 has an injector housing 52 that is typically
constructed from a plurality of individual parts. The housing 52
includes an outer casing 54 that contains block members 56, 58, and
60. The outer casing 54 has a fuel port 64 that is coupled to a
fuel pressure chamber 66 by a fuel passage 68. A first check valve
70 is located within fuel passage 68 to prevent a reverse flow of
fuel from the pressure chamber 66 to the fuel port 64. The pressure
chamber 66 is coupled to a nozzle 72 through fuel passage 74. A
second check valve 76 is located within the fuel passage 74 to
prevent a reverse flow of fuel from the nozzle 72 to the pressure
chamber 66.
The flow of fuel through the nozzle 72 is controlled by a needle
valve 78 that is biased into a closed position by spring 80 located
within a spring chamber 81. The needle valve 78 has a shoulder 82
above the location where the passage 74 enters the nozzle 78. When
fuel flows into the passage 74 the pressure of the fuel applies a
force on the shoulder 82. The shoulder force lifts the needle valve
78 away from the nozzle openings 72 and allows fuel to be
discharged from the injector 50.
A passage 83 may be provided between the spring chamber 81 and the
fuel passage 68 to drain any fuel that leaks into the chamber 81.
The drain passage 83 prevents the build up of a hydrostatic
pressure within the chamber 81 which could create a counteractive
force on the needle valve 78 and degrade the performance of the
injector 10.
The volume of the pressure chamber 66 is varied by an intensifier
piston 84. The intensifier piston 84 extends through a bore 86 of
block 60 and into a first intensifier chamber 88 located within an
upper valve block 90. The piston 84 includes a shaft member 92
which has a shoulder 94 that is attached to a head member 96. The
shoulder 94 is retained in position by clamp 98 that fits within a
corresponding groove 100 in the head member 96. The head member 96
has a cavity which defines a second intensifier chamber 102.
The first intensifier chamber 88 is in fluid communication with a
first intensifier passage 104 that extends through block 90.
Likewise, the second intensifier chamber 102 is in fluid
communication with a second intensifier passage 106.
The block 90 also has a supply working passage 108 that is in fluid
communication with a supply working port 110. The supply port is
typically coupled to a system that supplies a working fluid which
is used to control the movement of the intensifier piston 84. The
working fluid is typically a hydraulic fluid that circulates in a
closed system separate from the fuel. Alternatively the fuel could
also be used as the working fluid. Both the outer body 54 and block
90 have a number of outer grooves 112 which typically retain
0-rings (not shown) that seal the injector 10 against the engine
block. Additionally, block 62 and outer shell 54 may be sealed to
block 90 by 0-ring 114.
Block 60 has a passage 116 that is in fluid communication with the
fuel port 64. The passage 116 allows any fuel that leaks from the
pressure chamber 66 between the block 62 and piston 84 to be
drained back into the fuel port 64. The passage 116 prevents fuel
from leaking into the first intensifier chamber 88.
The flow of working fluid into the intensifier chambers 88 and 102
can be controlled by a four-way solenoid control valve 118. The
control valve 118 has a spool 120 that moves within a valve housing
122. The valve housing 122 has openings connected to the passages
104, 106 and 108 and a drain port 124. The spool 120 has an inner
chamber 126 and a pair of spool ports that can be coupled to the
drain ports 124. The spool 120 also has an outer groove 132. The
ends of the spool 120 have openings 134 which provide fluid
communication between the inner chamber 126 and the valve chamber
134 of the housing 122. The openings 134 maintain the hydrostatic
balance of the spool 120.
The valve spool 120 is moved between the first position shown in
FIG. 4 and a second position shown in FIG. 5, by a first solenoid
138 and a second solenoid 140. The solenoids 138 and 140 are
typically coupled to a controller which controls the operation of
the injector. When the first solenoid 138 is energized, the spool
120 is pulled to the first position, wherein the first groove 132
allows the working fluid to flow from the supply working passage
108 into the first intensifier chamber 88, and the fluid flows from
the second intensifier chamber 102 into the inner chamber 126 and
out the drain port 124. When the second solenoid 140 is energized
the spool 120 is pulled to the second position, wherein the first
groove 132 provides fluid communication between the supply working
passage 108 and the second intensifier chamber 102, and between the
first intensifier chamber 88 and the drain port 124.
The groove 132 and passages 128 are preferably constructed so that
the initial port is closed before the final port is opened. For
example, when the spool 120 moves from the first position to the
second position, the portion of the spool adjacent to the groove
132 initially blocks the first passage 104 before the passage 128
provides fluid communication between the first passage 104 and the
drain port 124. Delaying the exposure of the ports, reduces the
pressure surges in the system and provides an injector which has
more predictable firing points on the fuel injection curve.
The spool 120 typically engages a pair of bearing surfaces 142 in
the valve housing 122. Both the spool 120 and the housing 122 are
preferably constructed from a magnetic material such as a hardened
52100 or 440c steel, so that the hysteresis of the material will
maintain the spool 120 in either the first or second position. The
hysteresis allows the solenoids to be de-energized after the spool
120 is pulled into position. In this respect the control valve
operates in a digital manner, wherein the spool 120 is moved by a
defined pulse that is provided to the appropriate solenoid.
Operating the valve in a digital manner reduces the heat generated
by the coils and increases the reliability and life of the
injector.
In operation, the first solenoid 138 is energized and pulls the
spool 120 to the first position, so that the working fluid flows
from the supply port 110 into the first intensifier chamber 88 and
from the second intensifier chamber 102 into the drain port 124.
The flow of working fluid into the intensifier chamber 88 moves the
piston 84 and increases the volume of chamber 66. The increase in
the chamber 66 volume decreases the chamber pressure and draws fuel
into the chamber 66 from the fuel port 64. Power to the first
solenoid 138 is terminated when the spool 120 reaches the first
position.
When the chamber 66 is filled with fuel, the second solenoid 140 is
energized to pull the spool 120 into the second position. Power to
the second solenoid 140 is terminated when the spool reaches the
second position. The movement of the spool 120 allows working fluid
to flow into the second intensifier chamber 102 from the supply
port 110 and from the first intensifier chamber 88 into the drain
port 124.
The head 96 of the intensifier piston 96 has an area much larger
than the end of the piston 84, so that the pressure of the working
fluid generates a force that pushes the intensifier piston 84 and
reduces the volume of the pressure chamber 66. The stroking cycle
of the intensifier piston 84 increases the pressure of the fuel
within the pressure chamber 66. The pressurized fuel is discharged
from the injector through the nozzle 72. The fuel is typically
introduced to the injector at a pressure between 1000-2000 psi. In
the preferred embodiment, the piston has a head to end ratio of
approximately 10:1, wherein the pressure of the fuel discharged by
the injector is between 10,000-20,000 psi.
After the fuel is discharged from the injector the first solenoid
138 is again energized to pull the spool 120 to the first position
and the cycle is repeated. It has been found that the double
solenoid spool valve of the present invention provide a fuel
injector which can more precisely discharge fuel into the
combustion chamber of the engine than injectors of the prior art.
The increase in accuracy provides a fuel injector that more closely
approximates the square fuel curve shown in the graph of FIG. 3.
The high speed solenoid control valves can also accurately supply
the pre-discharge of fuel shown in the graph.
FIG. 6 shows an alternate embodiment of a fuel injector of the
present invention which does not have a return spring for the
needle valve. In this embodiment the supply working passage 108 is
coupled to a nozzle return chamber 150 by passage 152. The needle
valve 78 is biased into the closed position by the pressure of the
working fluid in the return chamber 150. When the intensifier
piston 84 is stroked, the pressure of the fuel is much greater than
the pressure of the working fluid, so that the fuel pressure pushes
the needle valve 78 away from the nozzle openings 72. When the
intensifier piston 84 returns to the original position, the
pressure of the working fluid within the return chamber 150 moves
the needle valve 78 and closes the nozzle 72.
FIG. 7 shows an injector 160 controlled by a three-way control
valve 162. In this embodiment, the first passage 108 is connected
to a drain port 164 in block 90, and the intensifier piston 84 has
a return spring 166 which biases the piston 84 away from the needle
valve 78. Movement of the spool 168 provides fluid communication
between the second passage 106 and either the supply port 110 or
the drain port 124.
When the spool 168 is in the second position, the second passage
106 is in fluid communication with the supply passage 108, wherein
the pressure within the second intensifier chamber 102 pushes the
intensifier piston 84 and pressurized fuel is ejected from the
injector 160. The fluid within the first intensifier chamber 88
flows through the drain port 164 and the spring 166 is deflected to
a compressed state. When the spool 168 is pulled by the first
solenoid 138 back to the first position, the second passage 106 is
in fluid communication with the drain port 124 and the second
intensifier chamber 102 no longer receives pressurized working
fluid from the supply port 110. The force of the spring 166 moves
the intensifier piston 84 back to the original position. The fluid
within the second intensifier chamber 102 flows through the drain
port 124.
Both the three-way and four-way control valves have inner chambers
126 that are in fluid communication with the valve chamber 132
through spool openings 134, and the drain ports 124 through ports
130. The ports inner chamber and openings insure that any fluid
pressure within the valve chamber is applied equally to both ends
of the spool. The equal fluid pressure balances the spool so that
the solenoids do not have to overcome the fluid pressure within the
valve chamber when moving between positions. Hydrostatic pressure
will counteract the pull of the solenoids, thereby requiring more
current for the solenoids to switch the valve. The solenoids of the
present control valve thus have lower power requirements and
generate less heat than injectors of the prior art, which must
supply additional power to overcome any hydrostatic pressure within
the valve. The balanced spool also provides a control valve that
has a faster response time, thereby increasing the duration
interval of the maximum amount of fuel emitted by the injector.
Increasing the maximum fuel duration time provides a fuel injection
curve that is more square and more approximates an ideal curve.
As shown in FIG. 4, the ends of the spool 120 may have concave
surfaces 170 that extend from an outer rim to openings 134 in the
spool 120. The concave surfaces 170 function as a reservoir that
collects any working fluid that leaks into the gaps between the
valve housing 122 and the end of the spool. The concave surfaces
significantly reduce any hydrostatic pressure that may build up at
the ends of the spool 120. The annular rim at the ends of the spool
120 should have an area sufficient to provide enough hysteresis
between the spool and housing to maintain the spool in position
after the solenoid has been de-energized.
Now referring to FIG. 8, a basic valve controller in accordance
with the present invention may be seen. This controller circuit is
relatively small, and as shall subsequently be seen, results in
lower system power consumption, and accordingly can be mounted
directly on the injector assembly itself. The circuit is intended
to be used with solenoids of the hereinbefore described fuel
injector by connection to the coils 202 and 200 of the two
solenoids 138 and 140. As shown in FIG. 9, coil 200 has its leads
connected to connections P1 and P2 of FIG. 8 and coil 202 has its
leads connected to connections P3 and P4 of FIG. 8. In addition,
the circuit of FIG. 8 is connected to a power source and source of
control signal through a connector J1, with connection J1-1 being
connected to the vehicle or engine battery, typically 12 or 24
volts in the case of large diesel engines. Connection J1-2 is
connected to the battery ground, and connection J1-3 is connected
to a control source for providing a control signal to the driver
circuit.
The battery voltage on line 204 is provided to a five-volt
regulator 206 which provides a five-volt supply voltage for various
devices in the circuit. Capacitor C1 is a smoothing capacitor for
the five-volt output, with resistor R2 providing a trickle load on
the regulator to prevent the five-volt output from drifting upward
in the relative absence of other loads. The voltage on line 204 is
also provided through diode D1 to solenoid coil connection P1 and
through diode D2 to solenoid coil connection P3. Capacitor C2, a
relatively large capacitor, provides a smoothing effect on the
battery voltage on line 204, thereby providing some protection
against transients when the solenoid coils are switched in and out
of circuit. Capacitor C5 and C6 provide a similar smoothing when
the respective solenoid coil is switched in circuit.
The remainder of the circuit of FIG. 8 is perhaps best described by
following the signal flow for a typical control signal applied to
the control line J1-3. When the injector is in the quiescent state,
the voltage on the control line 208 will be at the low state,
either held low by the microcomputer or other digital circuit
driving the same, or pulled low by the pull-down resistor R4. This
holds the Q output of the monostable multivibrator 210 low, which
in turn holds the output of the voltage translator 212 low, holding
n-channel power device Q1 off. At the same time, the Q output of a
similar monostable multivibrator 214 will also be low, having
previously returned to the low state of its prior monostable cycle.
This holds the input to the translation device 216 low, the output
of which holds the gate of power n-channel device Q2 low, holding
the device off. Thus, in this state, both power devices Q1 and Q2
are off, so that one lead of each solenoid coil is one diode
voltage drop below the battery voltage on line 204, with the
opposite coil connection of each coil essentially floating and thus
being at the same voltage as the first connection.
A typical signal format on line 208 is shown in FIG. 10. On the
positive going side of the pulse, the monostable multivibrator 210
is triggered, driving the Q output high which in turns drives the
output of the voltage translator 212 high, turning on the power
n-channel device Q1. This essentially grounds connection P2, so
that now the full battery voltage is connected across solenoid coil
200 (less one diode voltage drop of diode D1 and the on voltage
drop across power device Q1) pulling the spool towards solenoid 140
(see FIG. 4) to pressurize the intensifier chamber 102 and initiate
fuel injection. At the same time, the RC combination of resistor R1
and capacitor C3 determines the length of time the monostable
multivibrator 210 remains in the triggered state until returning to
the quiescent state with the Q output thereof low, thereby turning
n-channel power device Q1 off again to terminate current flow in
coil 200. In general, the pulse of the monostable multivibrator 210
is chosen to be equal to the actuating time, that is the transit
time for the spool from one stable position to the opposite stable
position, plus a time increment as a margin of safety to
accommodate adverse extremes in battery voltage, solenoid coil
resistance, temperature, etc., and further to accommodate bounce of
the spool when it reaches its new position. At the end of the
period of the monostable multivibrator 210 operation, the power
n-channel device Q1 is turned off, terminating the temporary
connection of solenoid lead P2 to ground. The resulting back EMF of
the solenoid coil forward biases zener diode Z1, with the current
in the coil rapidly diminishing to zero as the result of the energy
dissipation in the voltage drop of the diode and the resistance of
the coil.
Thus, the resulting current pulse in solenoid coil 200 will be
approximately as shown in FIG. 11. The current pulse lasts just
long enough to assure that the spool travels to the opposite
extreme of its travel and latches at that position to initiate
injection, plus of course some time margin of comfort, after which
the pulse is terminated. Similarly, at the end of the control pulse
of FIG. 10, the monostable multivibrator 214 is triggered, pulsing
power n-channel device Q2 on through voltage translator 216,
thereby returning the spool to its initial position to terminate
the injection of the fuel injector. As before, the monostable
multivibrator 214 will itself time out after a safe operating time
for the spool as determined by resistor R3 and capacitor C4,
thereby turning off power n-channel device Q2, with the resulting
current pulse in coil 202 decaying rapidly through the forward
biased zener Z2 during the decay period due to the back EMF of coil
202.
From the foregoing description, it may be seen that a simple pulse
control signal having a time period equal to the desired injection
time period may be provided to the circuit of FIG. 8, with the
simple control waveform being converted to a first latching current
pulse to initiate injection at the beginning of the injection
control signal and a second current pulse to assure latching to
terminate injection at the end of the injection control pulse. This
is to be compared with prior art solenoid actuated injectors
wherein power must be applied to the injector solenoid throughout
the duration of the injection control pulse. Because of this
continuous application of power during injection, the prior art
required solenoid operated valves of a size and power dissipation
capability adequate to absorb the full solenoid actuating current
for the longest injection time (or injection duty cycle) required
of the injector. The net result is that the solenoid valve of the
prior art is generally required to be much larger than with the
present invention, which in turn tends to slow the valve operation,
resulting in a slow injection rise time and, what is particularly
bad, a slow injection termination. In that regard, note that full
travel of the spool of the valve of the present invention injectors
will be achieved at approximately 218 (FIG. 11) while the current
in the respective solenoid is still rising, though power to the
solenoid coil is itself terminated shortly thereafter, again while
the current is still rising. If, on the other hand, the current was
not terminated before the end of the pulse of FIG. 10, the current
would continue to rise, even in the present invention, to
considerably higher levels, resulting in a much higher current for
a much longer period, increasing the power dissipation to excessive
levels, perhaps on the order of one to two orders of magnitude. To
avoid this problem, either expensive, relatively large and power
consuming current limiting circuitry would be required, or
alternatively the drive on the solenoid would need to be reduced so
that the average power consumption was tolerable, thereby very
substantially reducing the speed of operation of the solenoid valve
and thus of the injector. Accordingly, the valve controller circuit
of FIG. 8 is a highly efficient circuit for controlling valves such
as fuel injection valves, allowing high drive, very fast solenoid
operating current pulses while maintaining a low total power
consumption, allowing the use of small solenoids and avoiding
substantial temperature rise thereof above the already quite warm
environment of an operating engine.
Now referring to FIG. 12, another controller circuit illustrating
another aspect of the present invention may be seen. Like the
circuit of FIG. 8, this circuit operates from a low impedance
battery power supply with the battery voltage applied between
connector pins J1-1 and J1-2 of connector J1, and operates from a
control signal on connector pin J1-3 of connector J1, the control
signal being in the same form as illustrated in FIG. 10 with
respect to the circuit of FIG. 8. The solenoid coil connections,
however, are slightly different from those shown in FIG. 9, namely
the two solenoid coils 200' and 202' are connected in series as
shown in FIG. 13, with the common connection J2-3 being coupled to
the battery supply voltage on line 204.
In the circuit FIG. 8, as previously described, power is applied to
one of the two solenoids for a period of time adequate to assure
that the spool has been attracted to the respective solenoid so
that when the current pulse is removed, the retentivity of the
spool and the stationary parts of the respective solenoid will
provide a sufficient residual field strength to latch the spool at
that position. Thus, when the solenoid coil for the opposite
solenoid is energized, the spool will remain latched in the
previously energized position until the force of the newly
energized solenoid overcomes the force of the residual magnetism of
the latched solenoid, at which time spool motion will commence. As
soon as any gap is created between the spool and the end of the
solenoid from which it is moving away, the residual field due to
the retentivity will essentially collapse, allowing the spool to be
rapidly accelerated by the now already substantial force of the
solenoid being actuated. The net result is that not only is the
power consumption low for the system of FIG. 8, but also valve
operation is very fast. However, the exact timing of the beginning
of spool motion, the force of the actuated solenoid at the time
motion begins, etc., will vary somewhat dependent upon the amount
of retentivity in the spool and the stationary magnetic parts of
the solenoid, whether there was any bounce after the prior
actuating current pulse diminished, just how well the parts mate,
etc. Consequently, there can be some small spool valve and thus
injector timing variation unit to unit and for a given unit,
particularly over the operating temperature range of the unit and
the operating fluid of the unit (fuel or hydraulic fluid). The
embodiment of FIG. 12, on the other hand provides both a more
controlled release of the latched solenoid shortly after excitation
of the opposite solenoid, achieving both more precise time of
initiation of spool motion and a faster rising unbalanced magnetic
force to decrease the transit time of the spool in the spool valve
to increase the speed of injector valve operation. This is achieved
by a sort of snap action, wherein a current, typically limited in
magnitude, is provided to the coil of the latched solenoid,
typically simultaneously with the application of the actuating
current pulse to the coil of the other solenoid. This purposely and
controllably holds the latched solenoid until the field strength in
the other solenoid rises to a relatively high level, when the
current in the latched solenoid is then terminated. Now the
initiation of motion is more precise in time (crank shaft angle,
etc.) and the acceleration of the spool to the opposite latched
position is greater, providing faster injector operation,
The specific circuit shown in FIG. 12 provides the foregoing
described snap action only in one direction of operation of the
spool valve, specifically the turning off of the injector valve in
a typical fuel injection system, such as direct combustion chamber
injection in a diesel engine, as a sharp cutoff is particularly
advisable to minimize the amount of unburned or partially burned
fuel in the engine exhaust.
Referring specifically to FIG. 12, as before, a five volt regulator
206 is connected to the battery voltage on line 204 to provide a
five volt output for operation of various other circuits of the
Figure. Capacitors C8, C12 and C13 provide noise suppression on the
five volt line. The specific circuit shown is a clocked circuit
(though a corresponding free-running circuit may also be used).
Thus, an oscillator 300 provides a clock signal to counter-divider
302 which in turn provides a clock signal to counter-divider 304,
with an appropriate clock signal on line 306 being taken from an
output of either counter-divider as may be suitable for the
specific application. In general, the clock signal on line 306
should be sufficiently high so that the time period of one clock
cycle is of no particular significance to the overall timing
requirements of the system.
As before, when the signal on line 208 goes high (see FIG. 10),
monostable multivibrator 308 is triggered so that its Q output on
line 310 forming the data input to D flip-flop 312 goes high. Thus,
on the next clock cycle, the Q output of the D flip-flop 312 on
line 314 triggers a voltage translator 316 to turn on power
n-channel devices Q2 and Q3, which devices are connected in
parallel and have their sources connected to ground through a
parallel combination of low valued resistors R11 through R15. This
pulls the voltage on connector terminal J2-1 low, applying power to
solenoid coil 200' (FIG. 13) to pull the valve spool to solenoid
140 and latch the same at that position.
As with the circuit in FIG. 8, the monostable multivibrator 308
will time out after a time period determined by the combination of
capacitor C7, fixed resistor R29 and variable resistor R25, which
time out could be used as before to drive the Q output on line 310
low to turn off the power n-channel devices Q2 and Q3 to terminate
the current pulse. Instead, however, in this embodiment, the
voltage across the parallel combination of resistors R11 through
R15 is coupled through resistor R16 to the positive input of
comparator 318, the negative input of which is determined by the
setting of variable resistor R18. Resistor R16 and capacitor C3
provide high frequency noise suppression to the positive input of
the comparator 318, with resistor R17 and capacitor C4 providing
similar high frequency noise suppression to the negative input of
the comparator. The specific comparator used (LM339) has a grounded
emitter, floating collector NPN transistor output, with resistor
R19 pulling the output of the comparator high whenever the positive
input to the comparator exceeds the negative input. Thus, as the
current in solenoid coil 200' rises (much like the current in coil
200 is shown to rise in FIG. 11). The voltage across the parallel
combination in resistors R11 through R15 rises, triggering the
comparator at a level determined by the setting of variable
resistance R18 so as to allow the pull-up resister R19 to pull the
voltage on line 320 high to reset the D flip-flop 312, driving the
Q output thereof on line 314 low and thus the output of voltage
translator 316 low to turn off devices Q2 and Q3 based not on a
time-out, but rather upon the reaching of a predetermined desired
current.
The termination of the actuation pulse based on reaching a
predetermined desired solenoid actuation current as opposed to
merely a predetermined time-out of the current pulse has
substantial further advantages in terms of power consumption,
particularly as it relates to the size of the solenoid coils and
the amplitude of the current pulse which may be used without
substantially heating the coils, and particularly without
overheating the coils. In particular, the field strength pulling
the spool away from the other solenoid against the force of the
residual magnetism thereof is proportional to the current in the
solenoid coil being actuated. The force, on the other hand, is
proportional to the square of the current. Accordingly, while the
battery voltage on line 204 may vary dependent upon the state of
charge of the battery and other loads thereon, even momentary
loads, and the resistance of the solenoid coils unit to unit and
with temperature may vary quite significantly, the peak current
attained is an excellent guarantee that the spool has pulled away
from the opposite solenoid and completed its travel to the solenoid
being powered. Thus, if the battery voltage is low by ten percent,
and the solenoid resistance is high by ten percent, the rise time
on the current pulse generally in the form shown in FIG. 11 will be
slower, so that the current pulse will be longer in time before the
predetermined desired current amplitude is reached and the current
pulse is terminated. Thus, the circuit automatically adjusts for
the more widely varying parameters to limit the current pulse
amplitude only to that required to assure fast and reliable
operation of the spool valve of the injector.
In comparison, without the current shut-off based on amplitude of
the pulse, the current pulse width to actuate and latch a solenoid
would have to be at least as long as required under the worst of
conditions. Then in the case of a high battery voltage and low coil
resistance, the current pulse may climb well above the
predetermined necessary limit before terminating. Since the
instantaneous power dissipation in the solenoid coil is
proportional to the square of the current, considerable excess
power will be dissipated in the solenoid coil under these
conditions, providing substantial unnecessary heating of the
solenoid coil. In that regard, the difference in spool valve
heating between the controller of FIG. 8 and the controller of FIG.
12 when simulating fuel injection in an operating engine is
substantial, the heating of the spool valve above ambient
temperature being significant when operating under the controller
of FIG. 8 and insubstantial when operated with the controller of
FIG. 12, even when driven hard for high speed operation
thereof.
For the actuation of the opposite solenoid for return of the spool
valve to the original position using the controller of FIG. 12, the
circuit comprising devices 308', 312', 316', Q1, Q7 and 318'
operate in the same manner as the corresponding unprimed numbered
components hereinbefore described, the monostable multivibrator
308' being triggered on the negative going side of the control
signal on line 208 (see FIG. 10 for the control signal waveform).
However, the release of the spool from its latched position is
delayed until the field in the solenoid being actuated builds to a
substantial level, at which time it is then released, thereby
providing a sort of snap action for increased operating speed. In
particular, in this circuit, when the monostable multivibrator 308'
is triggered, the monostable multivibrator 322 is also triggered,
driving the Q output on line 324 low, thereby turning off
transistor Q6 through resistor R23. Since prior to the triggering
of the monostable multivibrator 322, the Q output thereof on line
324 was high, thereby holding transistor Q6 on through resistor
R23, the gate of the power n-channel device Q4 had been held low,
thereby holding the device off. Similarly, the power n-channel
devices Q2 and Q3 were also off, the actuating current pulse for
coil 200' being terminated before this time. Consequently, when the
monostable multivibrator 322 is triggered together with the
monostable multivibrator 308', the voltage on line 324 going low
turns off transistor Q6. Since at this instant the current through
power n-channel device Q4 was zero, the base voltage on transistor
Q5 is also zero, holding the same off. Consequently, pull-up
resistor R32 is free to pull the gate of power n-channel device Q4
high, turning the same on.
In general, the value of fixed resistors R10 and R21 as well as
variable resistor R22 are substantially higher than the
corresponding parallel combination of resistors R1 through R5.
Thus, although the current pulse in coil 202' is rapidly rising, a
corresponding current pulse in coil 200' is rising at a lower rate.
However, because the magnetic gap in the solenoid powered by coil
200' is substantially zero, whereas the magnetic gap in the
solenoid powered by coil 202' is at a maximum, the magnetic field
in the solenoid powered by the coil 200' may be caused to build
from the residual field at as high or higher a rate than the field
in the solenoid powered by the coil 202'. As a result, the spool
will remain latched as the field and thus the force in the solenoid
powered by coil 202' rises to quite a substantial level. Then when
the lower current in coil 200' through power n-channel device Q4
reaches a predetermined level, albeit still considerably lower than
the current in coil 202', the voltage drop across resistors R10,
R21 and R22 will become adequate to start to turn on transistor Q5,
pulling the gate voltage of power n-channel device Q4 lower so as
to limit the current therethrough and thus through coil 200' to a
level adequate to hold the base voltage of transistor Q5 at 1 VBE
above ground. Thus the current in coil 200' becomes clamped at a
moderate value, as even the moderate value provides a high latching
force because of the zero magnetic gap in the respective solenoid
magnetic circuit. Then, when monostable multivibrator 322 times
out, the Q output thereon on line 24 will go high, turning on
transistor Q6 to pull the gate voltage of power n-channel device Q4
low, turning the same off to quickly terminate the latching current
in coil 200', allowing the now high force in the solenoid powered
by coil 202' to very rapidly accelerate the valve spool to the
opposite position. Shortly thereafter, of course, monostable
multivibrator 308' will itself time out, after which the next clock
cycle will turn off power n-channel devices Q1 and Q7 to terminate
the current pulse in coil 202' after the spool has been latched in
its new position.
It will be noted that the circuit of FIG. 12 does not include the
back EMF suppression zener diodes Z1 and Z2 of the circuit of FIG.
8. Back EMF protection is provided, however, by the power n-channel
devices themselves, the IRF540 devices effectively having back EMF
zeners therein. In that regard, the zener diodes in the circuit of
FIG. 8 are forward biased by the back EMF so that the current pulse
tails decline slower than necessary, whereas the internal zener
devices in the power n-channel devices of FIG. 12 only conduct in
the reverse direction across the zener voltage, causing a more
rapid declining current pulse tail. If desired, each zener diode of
FIG. 8 might be replaced by two zeners in series and connected in
opposite polarity to achieve a more rapid current pulse
termination.
Now referring to FIG. 14, a still further embodiment of the present
invention may be seen. This embodiment illustrates a still further
aspect of the invention. In particular, in this embodiment, when
one solenoid is actuated, the opposite solenoid is used to sense
the position of the valve spool so that the actuating current pulse
may be terminated upon arrival of the spool at the actuated
position, or a short time thereafter after any bounce has decayed.
Further, this embodiment is microprocessor or single chip
microcomputer controlled, so that depending upon the programming
thereof injector valve control may be effected through the input to
the processor of a control signal such as that illustrated in FIG.
10, or at the other extreme, may itself be used to control injector
operation (injection timing and duration) of one or more, typically
multiple cylinder injection valves based on basic parameter inputs
thereto such as engine speed and "throttle" setting as well as
secondary inputs if desired such as engine temperature, atmospheric
conditions, etc. In that regard, the circuit of FIG. 14 illustrates
a control circuit for a single injector valve, though obviously
aspects of the circuit can be replicated for multiple valve
applications using other processor or microcomputer output lines
for the control thereof.
The circuit illustrated in FIG. 14 utilizes the same solenoid coil
connections as the circuit of FIG. 12, namely that shown in FIG.
13. In the embodiment shown, an intel 8751 single chip computer 400
operating under program control is used. The clock for the computer
is referenced to an external crystal oscillator comprising crystal
X1 and capacitor C1 and C2. Also, the RC circuit comprising
resistor 2 and capacitor 3 provides the appropriate reset pulse on
start-up of the computer. The specific embodiment shown is intended
to operate in response to the control signal of FIG. 10 applied to
the J1 connector lead J1-3. That input signal on line 208, normally
held low by pull-down resistor R1, is inverted twice by NAND gates
402 and 404 to apply the signal at appropriate signal levels to one
lead of one of the ports of the computer configured as an input
port for that purpose. Two leads of another port configured as an
output port provide signals on lines 406 and 408 to control voltage
translation devices 410 and 412, respectively, which in turn turn
on and off power n-channel devices Q1 and Q3, respectively, to
provide the desired current pulses to solenoid coils 200' and 202',
respectively.
To describe the operation of the circuit of FIG. 14, assume for the
moment that the control signal of FIG. 10 is low, that both power
n-channel devices Q1 and Q3 have been off for a sufficient length
of time for any current pulses in the respective solenoid coil to
have reduced to zero, and that the valve spool is latched at the
position last powered by solenoid coil 202' In this state, the
processor will hold line 406 low, holding power n-channel device Q1
off, line 408 low, holding power n-channel device Q3 off, and lines
414 and 416 high to hold transistors Q7 and Q10 on, respectively.
In that regard, the circuit comprised of resistor R5, transistors
Q7 and Q6, resistors R3, R4 and R6, and power n-channel device Q5
functionally duplicates the circuit of FIG. 12 comprising resistor
R23, transistors Q6 and Q5, resistors R22, R21, R10 and R32, and
power n-channel device Q4 of FIG. 12, providing the snap action
hereinbefore described. As described, this snap action allows the
previously actuated solenoid to initially hold the valve spool
until the newly actuated solenoid achieves a relatively high force
level, at which time the spool will be released, thereby improving
the speed of operation of the valve and repeatability with time and
unit to unit. In the circuit of FIG. 12, snap action was provided
in only one valve actuation direction, whereas in FIG. 14 the
circuit which provides snap action is duplicated so as to be
provided on each solenoid coil, thereby providing snap action in
both directions, the timing and the release being set under program
control by the processor or single chip computer. For providing the
same holding action on solenoid coil 202', the circuit is
duplicated by resistor R15, transistors Q10 and Q9, resistors R14,
R7 and R22, and power n-channel device Q8.
When the control signal on line 208 (FIG. 14) goes high indicating
injection is to begin, the processor pulls the voltage on line 406
high and the voltage on line 416 low. Pulling line 406 high turns
on power n-channel device Q1, pulling one end of solenoid coil 200'
low, thereby applying substantially full battery voltage
thereacross. At the same time of course, line 416, being pulled
low, allows pull-up resistor R22 to turn on power n-channel device
Q8 until the current therethrough builds to the point that one VBE
is applied to transistor Q9 to partially turn on the same and limit
the gate voltage of power n-channel device Q8 to limit the current
therethrough as previously described with respect to the
corresponding circuit of FIG. 12. Then, very shortly thereafter,
the processor drives the voltage on line 416 low again, turning on
transistor Q10 and turning off power n-channel device Q8 to
initiate valve spool motion. At this point, even though the holding
current in coil 202' rapidly decays, there is still a substantial
field strength in the respective magnetic parts of the solenoid
because of the absence of a non-magnetic gap in the respective
magnetic circuit. Thus, the field starts to diminish, generating a
voltage across coil 202' equal to ##EQU1## As the valve spool
begins to move, the rate of collapse of the field in what had been
the holding solenoid is accelerated because of the existence of an
increasing non-magnetic gap in the respective magnetic circuit.
This field collapse continues at an increased rate because of the
increasing speed of the valve spool, until the valve spool is
stopped at the extreme it was to travel. During most of the spool
travel, the current in coil 202' will have fallen to substantially
zero, the impedance of the circuits connected in parallel to
solenoid coil 202' being relatively high. Consequently, the voltage
generated in coil 202' is due primarily to two factors: one, the
collapse of the field of the magnetic circuit surrounding coil 202'
because of the increasing non-magnetic gap in that solenoid's
magnetic circuit and, two, some coupling of the magnetic field from
the opposite solenoid excitation. Generally speaking, the coupling
from the excitation of the opposite solenoid will be relatively
low, particularly as the spool approaches the end of its travel
because of the now small and decreasing magnetic gap in the excited
solenoid and the relatively large nonmagnetic gap in the solenoid
having a substantially open coil. When the valve spool stops at its
final position, what small residual magnetic field remains in the
non-excited solenoid becomes stable so that the rate of change of
field strength through coil 202' suddenly slows tremendously.
The net result of the foregoing is that once current is terminated
in the holding solenoid to initiate the snap action of the valve
spool toward the other solenoid, the back EMF in the solenoid coil
of what had been the holding solenoid may be sensed to provide an
accurate indication of the arrival of the valve spool at a fully
actuated position, which in turn may be used to terminate the
excitation to the driving solenoid coil. The net effect of this is
that all variables may be automatically accounted for, including
unit to unit variations, battery voltage variations, temperature
variations, etc. by determining the actual arrival of the valve
spool at the fully actuated position without any excessive drive on
the actuating solenoid coil which would result in unnecessary power
consumption and heating of the spool valve.
Referring now to FIG. 15, a strip chart showing the current
waveform 420 in an actuated solenoid and the back EMF 422 measured
on the coil of the solenoid which had previously been latched may
be seen. As the current 420 initially rises, the spool remains in
the latched position. Once the spool pulls away from the latched
position and begins moving, an increasing back EMF 422 is generated
in the coil of what had been the latched solenoid. That back EMF
continues to increase until it reaches a peak at the time of
arrival of the spool in the new latched position, at which time the
back EMF rapidly decreases. In the curve shown in FIG. 15, the peak
in the back EMF 422 was used to terminate the drive voltage and
thus current 420 in the excited solenoid, though even if the
current 420 was continued thereafter for a period, the decaying
back EMF once the valve spool reaches the new latch position will
still be similar to that shown in FIG. 15. Accordingly, the peak in
the back EMF curve 422 may be used as a direct indication of the
arrival of the spool at the new latched position, with the current
pulse to the other solenoid being terminated at that time, or
preferably a short time thereafter to allow for the settling of any
bounce of the spool at its new position.
The peak in the back EMF of solenoid coil 200' of solenoid 140
(FIG. 4) is sensed by the circuit comprising capacitors C4, C5 and
C3, resistors R8, R9, R10, R11, R12, R13 and variable resistor R23,
comparators 440 and 442, NAND gate 444 and diodes D1 through D4. In
that regard, diodes D1 and D2 clamp the positive input to
comparator 440 to a voltage range of no less than one forward
conduction diode voltage drop below circuit ground to no more than
one forward conduction diode voltage drop above the five volt power
supply. Diodes D3 and D4, on the other hand, limit the voltage
range of the negative input of comparator 442 to one forward
conduction diode voltage drop below circuit ground to one forward
conduction diode voltage drop above circuit ground. Both of these
voltage ranges extend beyond the voltage range of the opposite
input to the respective comparator, and accordingly the diodes do
not affect the inputs to the comparators around their switching
point.
When the back EMF of solenoid coil 200' is low or substantially
zero and substantially unchanging, capacitor C5 will discharge
through resistors R9 and R10 so that the positive input to
comparator 440 will be substantially at ground. The negative input,
on the other hand, will be at some voltage above ground by an
amount dependent upon the adjustment of variable resistor R23.
Accordingly, the output transistor of the comparator 440 will be
turned on, holding the output of the comparator low against the
pull-up resistor R12. This assures that one input to NAND gate 444
is low, making the output of the NAND gate 444 high independent of
the other input thereto, which output is coupled back to the
processor or single chip computer 400 as an input signal
thereto.
When the back EMF of coil 200' starts rising as the valve spool
starts pulling away from the respective solenoid, capacitor C3
couples the rising voltage through resistor R8 to the negative
input of comparator 442, assuring now that the output of comparator
442 is held low, thereby assuring that the output of NAND gate 444
remains held high irrespective of the output of comparator 440. As
the back EMF continues to rise, capacitor C4 couples the rising
back EMF to the positive input of comparator 440, capacitor C5
being a relatively small capacitor primarily for noise suppression
purposes. When the positive input to comparator 440 exceeds the
negative input to the comparator, signifying that the back EMF has
increased at an adequate rate and level to clearly indicate spool
motion, the output transistor of comparator 440 will be turned off,
allowing resistor R11 to pull the respective input to NAND gate 444
high. The output of the NAND gate still remains high, however,
because of the still low second input to the NAND gate. At the same
time, the negative input to comparator 442 rises somewhat also, the
extent of the rise being limited in any event to one forward
conduction diode voltage drop of diode D4, and is further limited
dependent upon the rate of increase of the back EMF by resistor R8
which is a substantially lower valued resistor than resistor R13.
Because of the relatively low value of resistor R8, the combination
of capacitor C3 and resistor R8 act as a differentiator in the
frequency range of interest, holding the negative input to
comparator 442 above ground when the back EMF is increasing, but
pulling the same negative when the back EMF goes over the top of
the curve shown in FIG. 15 and begins any decrease, thereby acting
as a peak detector.
When the back EMF does go over the top and decreases at all,
capacitor C3 will pull the negative input to comparator 442 low,
turning off the output transistor of comparator 442 and allowing
pull-up resistor R11 to pull the second input of NAND gate 444
high. Assuming the rise in the back EMF has been fast enough and
high enough to properly indicate spool motion as herein before
described, both inputs to NAND gate 442 will be high immediately
after the back EMF has peaked, thereby driving the output of NAND
gate 444 low to signal the processor or single chip computer that
spool motion has been sensed and that the spool has arrived at the
extreme of its travel. The processor may then use this signal to
turn off the actuating current pulse on coil 202' by driving the
voltage on line 408 low, either immediately after sensing the
arrival of the valve spool at the fully actuated position as in
FIG. 15, or alternatively a short time thereafter to allow for any
bounce to settle to assure proper latching by way of the
retentivity of the magnetic materials.
The circuit just described is replicated for the solenoid coil 202'
by capacitors C6, C7 and C8, resistors R16, R17, R18, R19, R20, R21
and variable resistor R24, diodes D5 through D8, comparators 446
and 448 and NAND gate 450. Accordingly, the circuit of FIG. 14
provides snap action in both directions of motion of the spool
valve, and actual sensing of the spool motion so that each
actuating current pulse may be quickly yet reliably terminated upon
arrival off the valve spool at the newly actuated position to
minimize heating in the solenoids independent of operating
conditions and parameters, thereby allowing a small solenoid valve
and a high operating current pulse to minimize the operating time
for the spool valve without substantial heating and particularly
overheating of the relatively small solenoid coils.
Note that not only does the processor or single chip computer 400
control the various aspects of the operation of the spool valve,
but that it essentially monitors the operation thereof also.
Accordingly, the computer may also accomplish other tasks. By way
of example, if the spool has any tendency to stick, the computer
can recognize the lack of arrival of the spool at an actuated
position within a predetermined maximum time period and shut off
the current pulse even though the valve has not yet responded,
thereby avoiding overheating and possible burnout of the solenoid
coil. It can also sense the repetition of such an occurrence and
temporarily or permanently stop attempting to actuate the spool
valve pending replacement of the spool valve or entire injector. If
a single computer is being used to control a plurality of injector
spool valves through the various lines of the various ports of the
computer, the computer can obviously identify the offending valve.
Further, since the computer knows when it initiated a solenoid
actuating current pulse, and the computer is again signaled when
this spool motion is complete, the computer can determine the
length of time it took for the actuation, and compare that time to
a standard time for present operating conditions, or monitor the
short term variations in the length of actuation time of each spool
valve controlled by the computer. This can be important, in that
significant short term variations in the actuation time of a spool
valve are suggestive of a deterioration in performance due to
contamination, corrosion, or other factors which, if not corrected,
could lead to an outright valve failure, as temperature, battery
voltage, etc., should not have a short-term effect on the spool
valve. Accordingly, the computer can maintain performance
statistics which can be interrogated and used at the time of
planned engine maintenance to avoid the necessity of later
unplanned maintenance.
Now referring to FIG. 17, a block diagram of one embodiment of fuel
injection system in accordance with the present invention may be
seen. This fuel injection system, primarily intended for multiple
cylinder engines, utilizes a master controller responsive to
various inputs to provide control signals to individual controllers
which in turn control an associated injector. In a typical system,
the master controller would normally be responsive to such inputs
as the throttle setting, the engine speed, engine temperature,
ambient air temperature and crankshaft position to establish the
timing of the start and duration of injection for each cylinder. In
such a system, the master controller would provide control signals
generally in the form shown in FIG. 10, with individual controllers
of the general type illustrated in FIG. 12, or other embodiments
described herein or variations thereof, being responsive to the
control signal to control the associated injector. If, by way of
specific example, the controller in accordance with FIG. 12 is used
for the individual controllers, the entire controller may be
mounted on the injector, or as a first alternative, the power drive
electronics may be mounted on the injector (or spool valve
therefor) with the single chip computer being mounted in a separate
control box controlled by the master controller. Also, as indicated
in the figure, while the master controller controls the individual
controllers which in turn control the respective injectors, the
injectors may in turn feed back information to the individual
controllers with respect to the required time of actuation for the
spool valve therein. The individual controllers may use the time of
actuation for the spool valves to accumulate statistics on injector
operation for communicating back to the master controller, which
may be interrogated through a diagnostics port on the master
controller either continuously for display or recording, or
periodically at the time of scheduled engine service.
Alternatively, of course, the individual controller could merely
pass on these spool valve operating time periods to the master
controller, with the statistics thereon being determined and
maintained at the master controller for diagnostic purposes.
The advantage of the configuration of FIG. 17 is that the
individual controllers operate from a control signal waveform which
is the same as the normal drive to prior art solenoid actuated
injector valves wherein the solenoid is excited for the full
duration of the valve injection period. While the normal drive for
a prior art solenoid valve would normally be of a higher voltage,
the waveform could be easily clipped, limited or otherwise
translated to the input voltage range of a single chip computer or
other drive circuit being used, so that injectors with individual
controllers could potentially be used in direct substitution of
prior art solenoid operated injection valves. Such a system would
not have the diagnostics capabilities hereinbefore explained unless
the controller of the prior art was also replaced by a
corresponding controller in accordance with the present invention,
either when the injectors were replaced or at any appropriate later
time as desired. In that regard, note that the speed of injection
and particularly the speed with which injection can be terminated
is not dependent upon the master controller, but rather the
individual controllers and the injectors, so that replacement of
prior art solenoid operated injectors with the injectors and
individual controllers of the present invention without changing
the central controller should still result in increased fuel
economy and lower emissions from the engine.
In the case of new engines and engines wherein the entire fuel
injection system may be changed, a single more powerful central
controller may be used as shown in FIG. 18. Here a single central
computer monitors the various parameters determining injection time
and duration and controls the drive electronic for the spool valves
of the individual injectors, the spool valves in turn providing
their own performance data back to the controller for display
through a diagnostic system and/or later retrieval by the
diagnostic system.
Referring again to FIG. 3 and the description relating thereto, the
advantages of the small pre-injection preceding the main injection
have been described. The present invention allows such
pre-injection by appropriate programming of the computer
controlling the spool valves on each injector. In particular, FIG.
11 shows the current pulse in one coil to actuate the spool valve
and latch the same so as to initiate injection, and the current
pulse in the opposite coil to return the spool valve to the
original position and latch the same to terminate injection. These
current pulses, however, can be closely spaced in time, or even be
somewhat overlapping, to have an initial very short injection
period, then followed by the full injection cycle again to provide
the pre-injection followed by normal injection. Further, the
current pulse to initiate pre-injection may be intentionally
shortened so that full spool valve motion to initiate injection is
not achieved before excitation of the opposing solenoid coil. In
that regard, it should be noted that, as previously described,
controllers of the present invention may sense the time required
for full actuation of the spool valve, either as measured from the
beginning of the actuating pulse, or in the case of snap action,
from the termination of the holding current allowing release of the
spool valve to initiate actuation. This time of spool valve
actuation may be measured during the normal injection cycle (as
opposed to during pre-injection). While this measured time will
vary dependent upon battery voltage, individual coil resistance,
temperature, etc., the time for full travel of the spool valve to
initiate injection effectively integrates the effect of all such
variables. Further, the general shape of the curve of spool valve
position versus time during actuation will be fixed, even though
the time base may be stretched or compressed dependent upon battery
voltage, etc. Consequently, one can determine the current actuation
pulse to cause less than full spool valve motion for pre-injection
as a percentage of the full normal injection current pulse as a
design parameter of the injection system, and then apply that
predetermined percentage to the last full injection cycle to
determine the current pulse for the next pre-injection cycle. In
this way, a carefully tailored pre-injection cycle may be achieved
in spite of variations of temperature, battery voltage, etc., as
such variations will be or can be made small (capacitive filtering
of battery voltage, etc.) between one injection cycle and the next
pre-injection cycle.
Battery voltage in a properly operating engine system will remain
within reasonable limits, and the present invention is particularly
tolerant of battery voltage variations because of its ability to
terminate the spool valve actuating current pulse as soon as spool
valve motion is complete and latching has been achieved. However
battery voltage during engine starting can drop drastically, though
good control of injection during starting of an engine,
particularly a cold engine, is still desired. Accordingly, for this
purpose, a boost voltage circuit may be utilized when the battery
voltage drops below some predetermined voltage, such as below a
normal operating voltage indicative of the operation of the starter
motor.
For this purpose, as shown in FIG. 19, a low voltage detection
circuit is connected to the battery supply line for the injection
system. Thus, when the battery voltage as supplied to the injection
system falls below some predetermined limit such as, by way of
example, 10 or 11 volts in a 12 volt (typically 12.6 volt) system,
or perhaps 22 volts in a 24 volt system, the output of the low
voltage detection circuit will enable the operation of a step-up
switching regulator which in turn provides a stepped up and
regulated output voltage VOUT to a valve supply switching circuit.
Step-up switching regulators in general provide a constant output
voltage VOUT independent of the input voltage, and are capable of
proper operation from a small step-up in voltage to stepping up of
the input voltage thereto by a substantial multiple. In that
regard, one of the advantages of the present invention is the fact
that the average power required for actuation of the spool valves
is relatively low, a very small fraction of that required by prior
art solenoid controlled injection valves, so that the power
capabilities required of the step-up switching regulator used with
the present invention is relatively modest, particularly
considering that the same may be operating the fuel injectors for a
relatively large diesel engine.
A full circuit of the type shown in FIG. 19 may be seen in FIG. 20.
Here, a current supplied by resistor 500 through a voltage source
502 is provided as the positive input to comparator 504. Voltage
source 502 may be a zener diode or other voltage source as are
readily commercially available. The negative input to comparator
504 is provided by voltage divider comprising resistors 506 and
508. In operation, voltage source 502 holds the positive input to
the comparator at the voltage of the voltage source. If the battery
voltage is sufficiently high, the divided down voltage on the
negative input to the comparator 504 will still be higher than the
voltage of voltage source 502 to hold the output of the comparator
on line 510 low. As the battery voltage decreases, voltage source
502 will hold the positive input to the comparator at the voltage
of the voltage source, whereas the voltage on the negative input
will decrease in proportion to the decrease in the battery voltage
until finally the positive input to the comparator 504 is higher
than the negative input, driving the output of the comparator on
line 510 high. If the battery voltage drops below the voltage of
voltage source 502, the voltage source will shut off. Now the
voltage on the positive input to the comparator will be
substantially equal to the battery voltage, though the negative
input to comparator 504 will be a voltage divided down from the
battery voltage, so that the positive input to the comparator is
still higher than the negative input, so that the comparator still
holds line 510 high.
The voltage from line 510 provides an enable signal to the
switching step-up regulator 512, in the embodiment shown a pulse
width modulation switching regulator integrated circuit. (Switching
regulators of various types, including pulse width modulation and
frequency modulation regulators, are well known in the prior art of
electronics and need not be described further herein). The output
of the pulse width modulation switching regulator integrated
circuit is coupled through line 514 to the base of transistor 516.
When the pulse width modulator 512 is enabled as a result of low
battery voltage, the output of the pulse width modulator 512 will
turn transistor 516 on and off at a constant frequency, but with a
duty cycle as required to maintain the voltage on line 518 at the
predetermined desired level as sensed by the feedback on line 520
to the pulse width modulator. In particular, when transistor 516 is
turned on, the current in inductor 522 rises linearly, building up
energy in the magnetic field of the inductor. When transistor 516
is turned off, the back EMF of inductor 522 forward biases diode
524 to provide a charging current pulse to capacitor 526 which in
turn delivers current to the valves through diode 528. If the
electrical load on such a system is relatively low, transistor 516
will be turned on with a relatively low duty cycle, so that little
energy builds in inductor 522 before the transistor is turned off.
As this energy is delivered to capacitor 526 through diode 524, the
current in inductor 522 will again fall to zero, diode 524
thereafter preventing reverse current flow from the output back to
the battery. On the other hand, if the electrical load on the
system is relatively high, transistor 516 may be turned on with a
much higher duty cycle so that when transistor 516 is turned off, a
higher current pulse is delivered to capacitor 526 through diode
524, with transistor 516 being turned on again to again replenish
the energy in the inductor even before the inductor current falls
to zero.
Because of the low energy requirements of the solenoids of the
present invention, switching regulators of a reasonable size may be
used to step up a battery terminal voltage of only a few volts to
the full desired operating voltage of the system. This assures
performance of the injection system at any battery voltage adequate
to turn over the engine for starting purposes. 0f course, when the
battery voltage in the circuit of FIG. 20 is sufficiently high, the
negative input to comparator 504 will exceed the positive input
thereto, driving the enable voltage on line 510 low to turn off the
pulse width modulator 512. This holds transistor 516 off, with the
battery power being supplied through diode 530 to operate the
valves. In this condition the current through inductor 522 will be
zero, as the forward conduction voltage drop of diode 520 will be
less than the forward conduction diode voltage drop required by the
two diodes 524 and 528.
While the present invention valves and control systems therefore
have been described with respect to fuel injection applications,
and then with respect to certain exemplary types of fuel injectors,
it should be noted that other types of fuel injectors may be used,
and the invention is also highly useful in applications other than
fuel injection, particularly where high speed, small size, low
power consumption or high reliability through self monitoring
capabilities are desired. In the claims to follow, the word
microprocessor is used in the general sense to refer to what are
sometimes referred to as microprocessors, microcontrollers and
single chip computers. Thus while certain exemplary embodiments
have been described and shown in the accompanying drawings, it is
to be understood that such embodiments are merely illustrative of
and not restrictive on the broad invention, and that this invention
not be limited to the specific constructions and arrangements shown
and described, since various other modifications may occur to those
ordinarily skilled in the art.
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